1. Field of the Invention
This invention relates to the repair of ball valves and, in particular, to an apparatus for inplace refinishing of the seating surfaces in top loaded ball valves.
2. Description of Prior Art
The seating surfaces of ball valves, particularly those used in controlling the flow of water or other materials under high pressure, are subject to damage due to the corrosive action of the material flowing through the valve or the cutting action of the high pressure flow. In the past, the leaking valves were cut from the system, taken to a remote location for repair, and then reinstalled. This procedure involves much time and expense, in part because the valves are often in relatively inaccessible locations and safety factors require a thorough examination of the installation joints (welded) and system testing.
U.S. Pat. No. 4,114,483 entitled "Portable Boring Tool for Ball Valves" discloses apparatus capable of refinishing the seating surface of ball valves in line. However, the apparatus described therein has some limitations. Each embodiment of the apparatus is suitable for use with only a single valve; a separate apparatus is required for valves of different sizes. The alignment of the apparatus on the valve is also subject to error. The apparatus is positioned independently for each face of the valve. Thus there is no assurance that each face is the same distance off center or even if the resurfaced faces are parallel. Proper position is assumed when each of a pair of locating buttons touches the valve face to be resurfaced. This method of alignment is somewhat uncertain, especially since the buttons are not visible during the installation of the apparatus. The uncertainty is increased when the buttons rest in a corroded area of the valve face.